As you can see, the file to be converted is simply read using "\input" and then converted
in the Lua function "processInputFile". By using coroutines, we can pretend to convert the file
in one go, when really we are supplying it line by line to LuaTeX.

It would of course be possible to check the file type/extension inside the "open_read_file" callback and perform different conversions (or none at all if a TeX file) depending on the
file type, i.e. to typeset source code.